如何以php格式提交html标签？

Question

表单是

    <form class="form-horizontal form-label-left" enctype="multipart/form-data" method="post" >

       <div class="form-group">
          <label class="control-label col-md-3 col-sm-3 col-xs-12">URL </label>
          <div class="col-md-9 col-sm-9 col-xs-12">
              <input type="text" class="form-control" name="uurl" placeholder="url" value="<?php echo htmlspecialchars($sql['url']); ?>">                          
          </div>
       </div>

       <div class="form-group">
          <div class="col-md-9 col-sm-9 col-xs-12 col-md-offset-3">
              <button type="button" class="btn btn-primary">Cancel</button>
              <button type="reset" class="btn btn-primary">Reset</button>
              <button type="submit" name="posted" class="btn btn-success" >Submit</button> 
          </div>
       </div>
</form>

<iframe width="640" height="360" src="https://www.youtube.com/embed/iZqDfqsOiRM
?modestbranding=1&rel=0&showinfo=0" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>

这个iframe代码我想通过表单发送到mysql db。 P.s如果我不使用这个iframe代码作为输入，表单工作正常。但我需要提交带有这些标签的表格

表单提交代码位于

之下

if(isset($_POST['posted'])){
  extract($_POST);
  $eid=$_GET['eid']; 
   if($mysqli_query($con, " UPDATE channel SET title = '$utitle', url = '$uurl', picture = '$upicture', datetime = '$udatetime', status = '$ustatus', type='$utype' WHERE id = '$eid' ")){
    echo '<script> alert("Record Updated"); </script>';
   } 
}